1. Field of the Invention
The present invention relates to a production method of a component-embedded substrate including an electronic chip component mounted in a substrate, and a component-embedded substrate.
2. Description of the Related Art
Various configurations in which an electronic chip component is mounted in a multilayer substrate including a plurality of dielectric layers have conventionally been proposed. For example, a printed substrate described in the Japanese Unexamined Patent Publication No. 2003-17859 is formed by a production process in which a plurality of thermoplastic resin sheets are stacked, and these sheets are integrated by hot pressing. During this production process, hot pressing is performed with an electronic chip component being held between the resin sheets and then the electronic chip component is embedded into the printed substrate to be fixed.
This printed substrate has a conductor pattern formed therein for connecting the electronic chip component to an external circuit. The conductor pattern and an external electrode of the electronic chip component are connected through a conductive via.
Such a connection configuration is implemented by the following production process.
The electronic chip component is disposed in a cavity formed of a concave part or a through-hole formed in the resin sheet. At least one of the resin sheets holding the electronic chip component is provided with a through-hole (via hole) at the position against which the external electrode of the electronic chip component abuts. The stacked plurality of resin sheets is hot-pressed with a conductive paste being filled in the through-hole and with the electronic chip component being held. In this case, the electronic chip component can be disposed as positioned to a desired location in the printed substrate due to the presence of the cavity.
The conductive paste is melted and sintered contacting with the external electrode of the electronic chip component and the conductor pattern. With this process, the external electrode of the electronic chip component and the conductor pattern are connected to each other through the conductive via.
In this process, more conductive paste is preferably filled in the through-hole. In addition, the conductive paste is preferably enough so as to rise from the surface of the through-hole. Filling the conductive paste as described above ensures the connection between the external electrode of the electronic chip component and the conductor pattern through the conductive via after the hot pressing.
However, the component-embedded substrate having the configuration described above has following problems. FIGS. 16A and 16B are views each for describing a problem of a component-embedded substrate having a conventional configuration. FIG. 16A is a side sectional view, and FIG. 16B is a plan view illustrating a plane where a conductive via and an external electrode of an electronic chip component are bonded.
The above component-embedded substrate having the conventional configuration is formed by hot-pressing a plurality of thermoplastic resin sheets. In this process, the conductive paste rising from the surface of the through-hole (via hole) and the conductive paste filled in the through-hole overflow from the through-hole with the pressing.
The cavity is formed to have an opening area slightly larger than the dimension of the electronic chip component due to the reasons such as facilitation of the insertion of the electronic chip component. Therefore, the overflowing conductive paste enters a gap between the electronic chip component in the cavity and a wall surface of the cavity. When the conductive paste is melted by an application of heat, its fluidity is increased. Accordingly, the melted conductive paste might flow over a wider range through the gap in the cavity. When the resin sheet is melted to fill the cavity with this hot press, the conductive paste flowing into the gap in the cavity might be sintered on the spot to remain around the electronic chip component.
With this, in a component-embedded substrate 10P having the conventional configuration, a first external electrode 31 of an electronic chip component 30 fixed in a resin substrate 20P and a conductor pattern 421 are connected to each other through a conductive via 521, and a second external electrode 32 of the electronic chip component 30 and a conductor pattern 422 are connected to each other through a conductive via 522, and in addition, the first external electrode 31 and the second external electrode 32 might be short-circuited with a leaking conductor 550 which flows and is sintered, as illustrated in FIGS. 16A and 16B.